The present invention relates to a cooling fan for motors, and more particularly to a cooling fan for motors in which two bearings or copper bushings and a closed shaft holder adapted for containing lubricant therein are provided, so that the cooling fan has reduced rotational resistance and less heat produced by the rotational friction, and, power consumption required by the cooling fan is also reduced.
FIG. 4 illustrates a conventional cooling fan for motors which mainly includes a back cover 1 having a shaft holder 11 provided at a central portion thereof. A bearing 3 is disposed in the shaft holder 11, a motor 9 is properly provided around an outer periphery of the shaft holder near a middle portion thereof with coils 91 wound about the outer surface of the shaft holder 11. When the motor 9 is turned on, a rotary shaft 23 extending into the shaft holder 11 and through the bearing 3 is rotated with the help of the bearing 3. The rotation of the rotary shaft 23 then drives a front cover 2 and blades 21 of the cooling fan to rotate.
Following drawbacks are found in the conventional cooling fan for motors having the above-described structure:
1. Since there is only one bearing 3 provided in the shaft holder 11, the rotary shaft 23 tends to rotate eccentrically and very possibly causes unstable rotation of the blades 21.
2. The rotary shaft 23 shall rotate at increased resistance when a part of lubricant in the shaft holder 11 is consumed and the only bearing 3 is worn out.
3. The increased resistance during the rotation of the rotary shaft 23 shall further increase the heat produced by the friction of shaft 23 with the bearing 3 and causes larger consumption of power.
It is therefore tried by the inventor to develop a cooling fan for motors to eliminate the above drawbacks existed in the conventional cooling fans.